Conventionally, light hydrocarbon oil has been used as base oil for lubricant, diluent or various solvents. More specifically, such hydrocarbon oil is used in, for example, metalworking oil for a variety of processing of various metals, electric discharge machining oil, rust preventing oil, wash oil, and various other solvents. Since improvement in working environments such as volatility, flammability, odor, and safety for irritating property to skin is needed in the use of such light hydrocarbon oil, a multifunctional hydrocarbon oil composition containing such hydrocarbon oil must satisfy various required performances according to the purpose of use in addition to the above-mentioned improvement in working environments. As concrete modes of such a multifunctional hydrocarbon oil composition, for example, metalworking oil, other metalworking oil, electric discharge machining oil, rust preventing oil, and detergent composition as described above can be given. The background art in the respective concrete modes or in a first mode to a fifth mode will be described.
First Mode (Metalworking Oil)
An aluminum fin used in a heat exchanger for a freezing and refrigerating system such as a refrigerator or air conditioner is produced by performing plastic working such as stretching, drawing, stamping, curling, or ironing to an aluminum fin material. Such working of the aluminum fin material is generally performed using a working lubricant, which is prepared by adding an oily agent of fatty acid, fatty acid ester, higher alcohol, α-olefin or the like to mineral oil or synthetic hydrocarbon such as isoparaffin (e.g., refer to Patent Literature 1). However, since such a working lubricant cannot provide sufficient lubricity, adhesion of aluminum to a punch or damage of the material surface can be caused. However, an increased addition amount of additives for solving this problem inhibits performances as fin such as water leakage, in addition to deterioration of the working environments by increased odor and occurrence of a problem in appearance such as discoloration due to imperfect oil removal by heat.
In metal rolling of aluminum and aluminum alloy, conventionally, higher alcohol, fatty acid ester, fatty acid, alkylene glycol ester compound, α-olefin and the like have been used as an oily agent of rolling oil, with higher alcohol being most general, followed by fatty acid ester (refer to Patent Literatures 2 and 3).
However, for improving the productivity, rolling of metal at higher rate and higher draft is required, resulting in exposure of a lubricated portion to a further high temperature. In rolling of high-purity materials with aluminum purity of 99%, 99.9% and more than 99.99%, which are generally called two nines, three nines, and four nines, remarkable adhesion inhibits lubricity, generation of a large amount of abrasion powder disturbs improvement in productivity.
Therefore, a sufficient rolling limit cannot be ensured by addition of a known oily agent, and measures to increase the addition amount of the oily agent or to reduce the rolling rate or draft have been taken. However, the increase in amount of the oily agent causes problems of deterioration of plate quality such as staining at annealing, slip between a work roll and a rolled material, uneven brightness of a rolled plate surface, or increase in amount of abrasion powder; deterioration of working environments by increased oil odor; rise of rolling oil cost, and the like. On the other hand, a reduced rolling rate or draft undesirably causes reduction in productivity.
Patent Literature 1: Japanese Patent Application Laid-Open No. 2-133495
Patent Literature 2: Japanese Patent Application Laid-Open No. 2003-165993
Patent Literature 3: Japanese Patent Application Laid-Open No. 2003-165994
Second Mode (Metalworking Oil)
In cutting/grinding, a cutting/grinding lubricant are generally used for the purpose of improving productivity in machining such as extension of life of a tool used for working such as a drill, an end mill, a bite or a grinding wheel, improvement in surface roughness of a workpiece, and improvement in working efficiency resulting therefrom.
The cutting/grinding lubricant is roughly classified to two types, or a water-soluble cutting/grinding lubricant used by diluting a surfactant and a lubricating component with water and a water-insoluble cutting/grinding lubricant mainly composed of mineral oil and straightly used without dilution. In general, the water-insoluble cutting/grinding lubricant is excellent in lubricating performance, and the water-soluble cutting/grinding lubricant is excellent in cooling performance.
However, the cutting/grinding lubricant effective for improvement of working efficiency also have undesirable points viewed from another side, and a typical problem thereof is environmental effect. The lubricant is gradually deteriorated during use regardless of whether it is water-insoluble or water-soluble, and finally laid in an unusable state. In the water-soluble lubricant, for example, generation of microorganisms reduces the stability of the solution, resulting in separation of components, or remarkably deteriorates the hygienic environment, and the lubricant becomes unusable. In the water-insoluble lubricant, an acidic component produced in the progress of oxidation corrodes a metallic material, or remarkably changes the viscosity, and the lubricant becomes unusable. Further, the lubricant is wastefully used by adhesion to chips or the like.
In such a case, the deteriorated lubricant is disposed, and a new lubricant is used. The lubricant discharged as waste needs various treatments for preventing adverse effects on the environment. For example, a cutting/grinding lubricant which is developed while giving priority to the improvement in working efficiency frequently uses a chlorine-based compound which may generate toxic dioxin in incineration treatment or the like, and thus needs removing treatment of such a compound. Therefore, a cutting/grinding lubricant free from chlorine-based compound is also developed. However, even a cutting/grinding lubricant free from such a toxic component still has the problem of environmental effects associated with heavy discharge of waste. The water-soluble lubricant needs an expensive high-level treatment since it may contaminate environmental water areas.
As an example in which it is difficult to attain both improvement in working efficiency and reduction in environmental load, the manufacturing field of nonferrous metallic parts used as automobile parts or home electric parts can be given. More concretely, although the water-soluble lubricant is generally used for processing of a nonferrous metallic part made of aluminum, aluminum alloy or the like, the metal is frequently dissolved in the waste solution after processing, and treatment of the waste solution requires an enormous cost for treatment of waste solution. Further, in the use of the water-soluble lubricant, strict and frequent management is needed since decay of the lubricant or corrosion of the part surface will be caused if a lubricant having an optimum pH is not used.
Thus, dry working or application of water-insoluble lubricant has been examined for solving the above-mentioned problems in the field of nonferrous metal working.
On the other hand, as a new working method, development of cutting minimal quantitative lubrication type cutting/grinding method is increasingly expanded. This method comprises performing cutting/grinding while supplying a minimal amount of lubricant of about 1/100000 to 1/1000000, compared with the usage of lubricant in general cutting/grinding, to a workpiece together with a compressed fluid (e.g., compressed air). According to this system, a cooling effect by compressed air can be obtained, the amount of waste can be reduced since the minimal amount of lubricant is used, and the environmental effect associated with heavy discharge of waste can be also improved. Therefore, this method can be expected not only as a working method of nonferrous metal but also as a working method of ferrous metal.
In the minimal quantitative lubrication method, it is desired that a work with satisfactory surface can be obtained even with a minimal supply amount of lubricant, and cutting/grinding can be efficiently performed with minimized wear of a tool or the like, and further high performances are thus required for the cutting/grinding working oil. From the point of waste disposal or working environments, it is also desired that the lubricant has excellent biodegradability.
Further, in the minimal quantitative lubrication method, it is extremely important to generate satisfactory oil mist. If the state of oil mist is poor, the quantity of oil reaching a working point becomes insufficient due to pipe clogging, easily causing deterioration of working efficiency or reduction of tool life. On the other hand, if the oil is excessively easy to be misted, the oil discharged is scattered to contaminate the working environments. In this case, also, since a loss of oil is caused by scattering of the oil mist, the quantity of oil reaching the working point becomes insufficient due to the loss of oil by scattering of oil mist, easily causing deterioration of working efficiency or reduction of tool life.
Further, since the lubricant is supplied as oil mist in the minimal quantitative lubrication method, a lubricant with poor stability adheres to a machine tool inner part, a work, a tool, a mist collector inner part or the like during use, causing a sticking phenomenon, which hinders the treatment property to deteriorate the working efficiency. Therefore, in the development of lubricant used for the minimal quantitative lubrication method, a lubricant hard to stick is desired
In view of such an actual condition, the present inventors proposed a metalworking oil composition for minimal quantitative lubrication method, which contains both ester oil and hydrocarbon oil having a specific kinematic viscosity (Patent Literature 4).
Patent Literature 4: Japanese Patent Application Laid-Open No. 2006-290163
Third Mode (Electric Discharge Machining Oil)
Electric discharge machining is a method for accurately working a workpiece by opposing an electrode (copper, graphite, etc.) to a conductive workpiece within an insulating medium while keeping a narrow space of several microns to several tens microns between the both, and supplying a voltage from a working power source in a pulse-like manner through the space, thereby causing electric discharge when the space between the electrode and the workpiece corresponds to an interval of starting electric discharge at the voltage.
The processing rate (processing efficiency) is a scale showing how much the capability of the power source can be brought out, and it is one of basic performances in electric discharge machining together with processing accuracy (shown by irregularities on a working surface, namely, surface roughness or contamination of the working surface by adhesion of a combustion residue such as oil by discharge or so-called staining/non-staining).
The electric discharge machining oil used as the insulating medium seriously affects not only the processing accuracy but also the processing rate, and plays important roles of scattering molten metal caused by electric discharge machining, discharging scattered working powders out of electrodes, cooling a heated part by electric discharge machining, restoring insulation between electrodes, or the like.
As the base oil of such electric discharge machining oil, in general, a hydrocarbon solvent such as mineral oil, normal paraffin or isoparaffin is used (Patent Literatures 5, 6 and 7).
Patent Literature 5: Japanese Patent Application Laid-Open No. 2001-115179
Patent Literature 6: Japanese Patent Application Laid-Open No. 2003-342595
Patent Literature 7: Japanese Patent Application Laid-Open No. 2005-154471
Fourth Mode (Rust Preventing Oil Composition)
In the field of metallic members such as a steel plate, a bearing or the like, rust preventing oil is generally applied to a produced member for preventing rusting.
As the rust preventing oil, in addition to those used only for simply preventing rusting, a cleaning rust preventing oil having a cleaning effect, and a multifunctional rust preventing oil such as a rust preventing-working oil having both an effect of preventing rusting of an intermediate product and a lubricating effect in the following working process are known. In these rust preventing oils, base oil having a relatively low viscosity or base oil obtained by mixing low-viscosity base oil with high-viscosity base oil is frequently used.
Fifth Mode (Detergent Composition)
A metallic part generally generates abrasion powder since it is subjected to a metal working process such as cutting, grinding, or press working. The abrasive powder causes a lack of oil film, leading to rusting, since the abrasive powder itself easily rusts and easily absorbs an oil content such as rust preventing oil. The abrasion powder or dust left on a steel plate used for an automobile body or the like may cause a problem of flawing during press molding. Therefore, a cleaning process is unavoidable for the metallic part for various reasons described above (Patent Literatures 8 and 9).
Patent Literature 8: Japanese Patent Application Laid-Open No. 2003-238994
Patent Literature 9: Japanese Patent Application Laid-Open No. 2003-238995